1. Field of the Invention
The invention relates to an instrumentarium for repositioning and fixing of pertrochanterous and subtrochanterous fractures, comprising at least one bone nail of resilient material, which nail is bent at least at its proximal end portion and which is insertable into the medullary canal of a bone through an impact hole formed in the bone and which abuts under tension with its apex of curvature the wall of the medullary canal opposing the impact hole, the distal end of the bone nail being provided with a coupling member allowing a non-rotatable connection with an impact tool, an insert member insertable into the impact hole having a guiding channel for the bone nail to be driven in and for the at least partial accommodation of the coupling member of the bone nail, the insert member further being provided with a fixing means preventing its shifting in the impact hole and with a closure member for closing the guiding channel.
2. Description of the Prior Art
It is known to reposition and to fix pertrochanterous and subtrochanterous fractures by opening the medullary canal of the bone through an impact hole and by introducing into this impact hole at least one bone nail, conveniently several bone nails consisting of elastic material and being bent at least in its (their) proximal area. When introducing such bone nails into the medullary canal, the nails, under tension due to their elasticity, contact the wall of the medullary canal opposing the impact hole, so that on the proximal point of each nail arriving at the site of the fracture, the nail passes beyond this fracture into the condyle of the bone and fixes the fracture. By rotating the individual nails, the bone portions can be reduced so that they assume the correct relative position at the site of the fracture. For this purpose, the distal end of each nail is provided with a coupling member allowing a wholly non-rotatable connection with an impact tool. It is known to give this coupling member the shape of a small plate-like flattening U.S. Pat. No. 4,055,172), although other embodiments of the coupling member are possible. When the known nails are correctly positioned in the medullary canal, the nail ends protrude from the impact hole and the coupling member abuts under tension the outer surface of the bone distally of the impact hole, so that there exists the danger, particularly for older persons having porous bones, that the bone may collapse at the abutment site and moreover the sinews and muscles extending above the impact hole will be irritated by the protruding distal nail ends.
As a rule, the impact hole is made such that the bone is first punctured and subsequently the small hole thus formed is widended by means of a three- or four-edged reamer, enlarged by means of a chisel or by means of a drill. In all these cases, parts of the bone can be split off, thus enlarging the impact hole in an undesired manner. But also when forcibly driving the nails, a cortical wedge can be split off the proximal cortex by tangential shearing stress, which results in an undesired enlargement of the impact hole so that the edge of the impact hole can also collapse on its front side. Both cases result in the nails protruding in an uncontrolled manner and if the fracture extends into the bone, a torsional fracture of the femur may be produced by the surgeon.
It can also occur that the bone nails are driven too far into the impact hole so that the coupling member no longer abuts the outer surface of the bone or that the coupling member abutting the outer surface of the bone shifts towards the medullary canal because part of the edge of the hole has been broken off.
If the coupling member enters the interior of the medullary canal and thus disappears within the bone, this invariably results in the drawback that the required tension stress of the nails is reduced and the desired effect is thus no longer assured. If the whole nail is located within the medullary canal, it may be caught by the spongiosa bubbles present in the medullary canal and thereby prevented from sliding distally. If in such a case the bone is loaded so that the bone portions are brought closer together at the fracture site, the nail tip may perforate the condyle of the bone and penetrate into the socket of the hip joint (acetabulum). If nails having wholly entered the medullary canal are not caught by the spongiosa bubbles, the nails slide in distal direction and can then be removed only with great difficulty. For removing such nails, the impact hole must be enlarged to such an extent that the distal end of the nail located within the medullary canal can be seized.
In order to prevent these difficulties, it has been proposed to provide an insert member insertable into the impact hole and provided with a guiding channel for the bone nail to be driven in and for the at least partial accommodation of the coupling member of the bone nail and fixed to the bone by a fixing means, for instance a screw. After insertion of the bond nail(s), the insert member is closed by means of a lid-shaped closure member preventing the shifting of the distal nail ends out of the insert member (U.S. Pat. No. 4,467,793). The disadvantage of this known embodiment resides in the fact that the bone nails shift in the medullary canal until their distal ends abut the side of the closure member facing the guiding channel where the position of the bone nails is fixed. On loading the bone, however, the bone fragments are brought close together at the fracture site and it is then convenient to shift the bone nails in a distal direction in order to prevent the nail tip from perforating the condyle, although the shifting must not be so great as to disturb the function of the bone nails.